It is expected that fuel cells will play a significant role in a future sustainable energy system due to their high energy efficiency and possibility to use as renewable fuels. Fuels, such as biogas, can be produced locally close to the customers. The improvement for fuel cells during the past years has been fast, but the technology is still in the early phases of development; however, the potential is enormous. A computational fluid dynamics (CFD) approach (COMSOL MULTIPHYSICS ) is employed to investigate effects of different fuels such as biogas, prereformed methanol, ethanol, and natural gas. The effects of fuel inlet composition and temperature are studied in terms of temperature distribution, molar fraction distribution, and reforming reaction rates within a singe cell for an intermediate temperature solid oxide fuel cell. The developed model is based on the governing equations of heat, mass, and momentum transport, which are solved together with global reforming reaction kinetics. The result shows that the heat generation within the cell depends mainly on the initial fuel composition and the inlet temperature. This means that the choice of internal or external reforming has a significant effect on the operating performance. The anode structure and catalytic characteristic have a major impact on the reforming reaction rates and also on the cell performance. It is concluded that biogas, methanol, and ethanol are suitable fuels in a solid oxide fuel cell system, while more complex fuels need to be externally reformed.